1. Field of the Invention
The present invention relates to an image pickup apparatus for picking up an object image.
2. Related Background Art
Digitization has being progressed in various medical fields. Also in the X-ray diagnostic field, two-dimensional image pickup apparatuses have been developed to digitize images. Large image pickup apparatuses 43 cm in size at maximum are provided for mammography and chest radiography.
A large X-ray image pickup apparatus is realized by bonding, like tiles, four sensor panels using an amorphous silicon semiconductor formed on a glass substrate which is easy to increase its size. This adopts a technique for forming and using a large substrate for amorphous silicon semiconductor devices (large substrate, technique of forming elements on the substrate, and the like) which has already been established for LCDs (Liquid Crystal Displays). An example of this technique is disclosed in U.S. Pat. No. 5,315,101. FIG. 1 shows a large active array matrix disclosed in this reference. Referring to FIG. 1, this active array matrix comprises substrates 1901, pixels 1902, connection leads 1903, and common terminals 1904.
A large X-ray image pickup apparatus is manufactured by using a plurality of single-crystal image pickup elements (silicon or the like). Examples of this technique are disclosed in U.S. Pat. Nos. 4,323,925 and 6,005,911. Examples of single-crystal image pickup elements are CCD image pickup elements, MOS image pickup elements, and CMOS image pickup elements. Each image pickup element has performance which satisfactorily copes with an X-ray moving picture.
FIG. 2 shows an image sensor disclosed in U.S. Pat. No. 4,323,925. Referring to FIG. 2, an image 2003 of an object 2001 is formed on a surface 2004 via a lens 2002. Successive optical sub-images 2005 are reduced by tapered FOPs (Fiber Optic Plates) 2006 and incident on image input surfaces 2007. Image sensor modules 2008 have non-image pickup peripheral regions 2009 to which lead lines 2010 can be connected.
The prior art shown in FIG. 1 suffers the following problems.
Only a maximum of four (2xc3x972) sensor panels can be used to form one image because external terminals are connected to the peripheral portion to externally connect a driving circuit.
In addition, the scale of a signal processing circuit mountable on an image pickup element is restricted to allow a pixel to have only a pixel selection switch. Signal processing circuits (driver, amplifier, and the like) are externally connected.
Amorphous silicon, which is not good in semiconductor characteristics with respect to high-speed operation, is difficult to form a large image pickup apparatus which copes with a moving picture. An amorphous silicon image pickup element, which is lower in sensitivity than a single-crystal silicon image pickup element, is difficult to cope with an X-ray moving picture which requires high sensitivity.
The prior art shown in FIG. 2 has the following problems.
Each image pickup element is small (wafer size is 8xe2x80x3 at maximum by the current technique), so that 2xc3x972 or more image pickup elements are required.
In a simple large image pickup apparatus using many single-crystal image pickup elements, a dead space is inevitably formed at a bonding portion between respective image pickup elements (regions for arranging peripheral circuits such as a shift register, amplifier, and the like, external terminals for exchanging external signals and power, and a protection circuit are necessary separately from a pixel region). The dead space appears as a line defect, thereby degrading the image quality. To prevent this, a tapered FOP (Fiber Optic Plate) is used to guide light from a scintillator to an image pickup element while detouring the dead space. However, extra FOPs increase the manufacturing cost. Especially a tapered FOP is very expensive.
Light from the scintillator is difficult to enter the tapered FOP depending on the taper angle. The output light quantity decreases, and the sensitivities of image pickup elements lower, thereby decreasing the sensitivity of the overall apparatus.
It is an object of the present invention to provide an image pickup apparatus having an optimal circuit arrangement.
To achieve the above object, according to an aspect of the present invention, there is provided an image pickup apparatus comprising an image pickup region where a plurality of pixels which include photoelectric conversion units are arranged to pick up an object image by dividing the object image into a plurality of regions, and a scan circuit arranged between the plurality of photoelectric conversion units in said image pickup region to commonly process the plurality of pixels or/and signals from the plurality of pixels.
According to another aspect of the present invention, there is provided an image pickup apparatus comprising an image pickup region where a plurality of pixels which include photoelectric conversion units are arranged to pick up an object image by dividing the object image into a plurality of regions, and a common processing circuit arranged between the plurality of photoelectric conversion units in the image pickup region to selectively transfer, to a horizontal output line, signals from a vertical output line to which signals from a plurality of pixels in a vertical direction are read.
According to still another aspect of the present invention, there is provided an image pickup apparatus for dividing an object image into a plurality of regions to form one image, wherein external terminals which are connected to a wiring line sandwiched between boundary sides of first and second regions and are arranged in the first region, are not at the same positions in a direction along the boundary sides as external terminals which are connected to another wiring line sandwiched between the boundary sides and are arranged in the second region.